No answer here, I'm just trying to get educated on the premise behind the original question.
The modification prompting the requirement for conducted emission testing is the addition a USB device powered from the PC USB host. I assume this device consumes on the order of 1 Watt of power. The incremental increase in load on the power supply is therefore on the order of 1%. The dB increase in power supply differential mode conduced emissions is therefore 10*log (1.01) = 0.04 dB This is well within the uncertainty range. Are my assumptions incorrect or what crucial information am I missing that drives the need for requalifying ac mains conducted emissions? I (perhaps naively) thought that this modification would have required a radiated emissions rescan because of the new USB interface and cable, or perhaps conducted emissions testing on the USB cable utilizing an absorbing clamp. It is not at all obvious to me how the addition of the USB interface necessitates a mains conducted emission test. > From: "Robert A. Macy" <[email protected]> > Date: Thu, 06 Oct 2005 07:52:47 -0700 > To: [email protected] > Cc: [email protected] > Subject: Re: Conducted emission testing for FCC & CE. > > It is my opinion that you must test conducted emissions at > both AC input conditions, and archive those test results. > > > The mechanisms for conducted emissions can vary greatly > whether you're at 110/60 or 230/50. Better test. A good > Power Supply will minimally exhibit that effect, but who > knows if you have that one. > > Radiated is *very* unlikely to vary due to the AC mains, > however it can still change at the low end, but I've not > seen that happen much. > > Why balking at doing such a simple, short test? > > - Robert - > > On Thu, 6 Oct 2005 08:46:33 +0530 > [email protected] wrote: >> Dear Experts, >> Our product is a USB device connected to the PC >> USB host and >> operates at 5 volts D.C supply provided by the host >> system. Both FCC & CE >> insists that conducted emission testing is required for >> this kind of >> devices, with emissions measured at the a.c input side. >> Is it necessary to >> run 2 tests, one with a 230 volts 50 Hz a.c supply (for >> CE) and the other >> with 110 volts 60 Hz a.c supply (for FCC)? >> >> >> Sincerely >> >> K.Balasubramanian >> Project Leader - Hardware. >> >> - > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > Instructions: http://listserv.ieee.org/listserv/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Scott Douglas [email protected] > Mike Cantwell [email protected] > > For policy questions, send mail to: > > Jim Bacher: [email protected] > David Heald: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc > - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
